If you are only doing an extra hour, she shouldn't need anything besides what you've been sending. And honestly, if you are going during your lunch, I bet the bottle in the middle will be cut out. I'd still bring it JIC. I nursed on one side for my breaks and pumped on the other, but I had 9 hour days.

My first DD didn't take bottles at all at daycare. I nursed her at dropoff and pickup and over my lunch break and she was fine. My second DD did take bottles, but I kept up the same type of routine with her. She took bottles of 2.5 oz each at that age. She moved up to 3 oz around 7 months and never went higher than that. I would recommend sending smaller bottles rather than bigger ones, especially if you intend to nurse her when you arrive. For 4 hours, I might send two 2-2.5 oz bottles, just in case, but expect them to only use one.

I found this article really helpful: http://www.kellymom.com/bf/pumping/milkcalc.html
It has a calculator to help you figure out howmuch. I had the dr. telling me DS should be taking 4-6oz, but really with the amount of times he bf he really only needs 3-4oz. Saved me a lot of stress and wasted milk b/c he does not like the bottle!

I have sent 3 4 oz bottles for my dd since 3 months of age. She is 9 months now and I have never sent more- I just can pump any more than that anyway! I was told by a LC that 4 ozs is a good amount and should never really need more. They comfort suck so if the bottle is there sure they will eat more. When my DD finishes she may fuss but then she is given her pacifier and she is fine! Its hard to figure out how much especially when you can only pump a certain amount!

I send what I've pumped which is about 12-15 oz. total (among 3 bottles - it was 4 when she was younger). At around 6 months she was getting hungry during day so I ok'ed daycare to give her oatmeal w/ breastmilk in the morning if she was still hungry after her first bottle for them.